． （ ）

A 24种 B 12种 C 16种 D 8种

A b>0，c>0 B b>0，c<0 C b<0，c>0 D b<0，c<0 <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183530_9154.png" width="142" height="166" /> 

A {2，4｝ B {2，4，6｝ C {1，3，5} D {1，2，3，4，5，6}

A 8π B 4π C 2π D <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183602_5717.png" width="21" height="38" />

A <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184326_2279.png" width="35" height="21" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184330_9467.png" width="35" height="20" /> C 4 D 2

A <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184336_3060.png" width="18" height="37" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184340_5092.png" width="40" height="37" /> C <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184343_9935.png" width="40" height="38" /> D <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184347_7435.png" width="18" height="38" />

A <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183518_5248.png" width="107" height="39" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183513_8373.png" width="81" height="39" /> C <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183508_3841.png" width="81" height="38" /> D <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183500_2123.png" width="107" height="39" />

A 奇函数，且在(0，+∞)单调递增 B 偶函数，且在(0，+∞)单调递减 C 奇函数，且在(-∞，0)单调递减 D 偶函数，且在(-∞，0)单调递增

A 100 B 40 C 10 D 20

A 甲是乙的充分条件但不是必要条件 B 甲既不是乙的充分条件也不是乙的必要条件 C 甲是乙的充要条件 D 甲是乙的必要条件但不是充分条件